The present study was carried out at Krishi Vigyan Kendra, Lakhimpur, Assam to know the yield gaps between improved package of practices (IP) under Front Line Demonstration (FLD) and farmer’s practice (FP) of rapeseed and mustard crops. The study found that the yield of rapeseed – mustard in IP under irrigated conditions ranged from 9.8 to 10.8q/ha whereas in FP it ranged between 6.2 to 6.5 q/ha. The per cent increase in yield with IP over FP was recorded in the range of 36.73 to 41.67. The extension gap and technological index were ranging between 3.6- 4.5q/ha and 10.0-18.33 per cent, respectively. The trend of technology gap reflected the farmer’s cooperation in carrying out demonstrations with encouraging results in subsequent years. The cost benefit ratio was 2.5-3.2 under demonstration, while it was 1.8 to 2.2 under farmers practice. By conducting front line demonstration of proven technologies, yield potential of rapeseed and mustard crops could be enhanced to a great extent with increase in the income level of the farming community

Keyword: Front line demonstration; Rapeseed-mustard; Extension gap; Technology gap; Yield gap;